Method and systems for paging a radiotelephone unit based on the unit&#39;s current cell location

ABSTRACT

In the transmission of a message (LU) from a subscriber station (MS), a cell recognition signal (e.g. CI 2 ) identifying the current radio cell (e.g. C 2 ) in which the subscriber station (MS) is located is transmitted towards the mobile radio system with it and stored in a subscriber database (NVLR) of the mobile radio system. The stored cell recognition signal (e.g. CI 2 ) makes it possible to call the subscriber station (MS) via a radio message to the most recently used radio cell(s) (e.g. C 2 ) and possibly also to its/their neighboring radio cells. This reduces the signaling load on the transmission of the radio message (effective paging) in the area where there are radio cells. It is possible to derive the location information on the radio cell plane, which consists of the cell recognition to identify the radio cell last used by the subscriber station, without any additional signaling load.

BACKGROUND OF THE INVENTION

The invention relates to a method and a system for sending a radiopaging message to radiotelephone subscriber stations of mobileradiotelephone subscribers of a cellularly constructed mobileradiotelephone network.

In cellular mobile radiotelephone networks, the location ofradiotelephone subscriber stations of the mobile radiotelephonesubscribers are managed on the basis of location areas (location areas)that are respectively assembled from one or several radio cells and thatcan be identified by means of an associated location area identifier(location area identity). From the system specification “D900 MobileCommunication System,” by Huder/Geier, Siemens AG 1992 (order numberA30808-X3231-X-2-7618), a cellularly constructed digital mobileradiotelephone network is known that is operated according to the GSMstandard (Global System for Mobile Communication). In the case of thesetup of a connection to the radiotelephone subscriber stations, e.g. onthe basis of a call initiated from another network and directed to themobile radiotelephone subscriber (mobile terminated call), a radiopaging message is transmitted into all radio cells of the location areain which the called mobile radiotelephone subscriber is located with hisradiotelephone subscriber station (paging). The radio paging messageserves to prompt the mobile radiotelephone subscriber to registerhimself with his radiotelephone subscriber station in the network, or,respectively, at the installations thereof—the responsible basetransceiver station. Due to the fact that the radio paging message mustalways be transmitted to all the radio cells of the known location area,a high load arises both for the concerned installations of the mobileradiotelephone network that are involved in the signaling and also forthe signaling channels in the radio cells. In the radio cells, thepaging message is sent on control channels. The signaling load increasesproportionally given an increasing number of radio cells in a locationarea.

From the international patent application WO93/23965, a cellularcommunication system is known in which a radio paging message can betransmitted to radiotelephone subscriber stations within a service area(service area) (paging). Paging regions are thereby defined that consistof a multiplicity of location areas (location areas). The paging messageis first transmitted to the location area, and is subsequentlytransmitted into the larger paging area for the case in which the radiopaging message remains unanswered. An item of information for theidentification of the current location area is transmitted to thecommunication system by each radiotelephone subscriber station.

From the international patent application WO94/07337, a cellular mobileradiotelephone network is known in which a subscriber-specific andtemporary paging area is defined for a radiotelephone subscriber stationthat is moving in a particular cell of a paging area consisting of oneor several radio cells. A timer thereby starts for the selectedradiotelephone subscriber station as soon as it goes into the pagingarea, and an initialization message is activated after the elapsing of apredeterminable time duration. This message causes the network to definethe temporary paging area and to store it in a subscriber database ofthe network. The smallest paging area comprises only a single radiocell.

SUMMARY OF THE INVENTION

The object of the present invention is to indicate a method and a systemof the type named above that enables a more effective paging.

Accordingly, in the transmission of messages sent respectively by theradiotelephone subscriber station, a cell identifier that identifies thecurrent radio cell in which the radiotelephone subscriber station islocated is concurrently sent, in addition to the location areaidentifier, in the direction of the mobile radiotelephone network, andis stored in a subscriber database of the mobile radiotelephone network.In addition, the cell identifier is entered in a list of cellidentifiers on the basis of which the radio paging message is sent. Thismeans that an item of information concerning the radio cell used by themobile radiotelephone subscriber or, respectively, the radiotelephonesubscriber station can be obtained without additional signaling traffic.The derivation of the location information on the radio cell level thusensues without increasing the signaling load. Rather, there is indeed areduction of the signaling load during the transmission of the pagingmessage (paging), due to the fact that, on the basis of the cellidentifiers stored in the list, a paging is carried out to the last-usedradio cell or cells, and, if warranted, additionally to the radio cellsadjacent thereto. Especially for radiotelephone subscriber stations withrapidly successive interactions with the mobile radiotelephone network(in particular given the transmission of data packets according to aseparate packet data service (General Packet Radio Service)), or forquasi-stationary radiotelephone subscriber stations (which, likewire-bound subscriber stations, are located for a longer period of timeat the same location), the probability of a change of radio cell is low.For this reason, the effective paging to the last-used radio cell orcells that can be identified by the corresponding cell identifiers leadsto a reduction of the signaling load and to an increase of the radiotransmission capacity during the transmission of the radio pagingmessage within the respective location area.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawings, in the several Figures of which like referencenumerals identify like elements, and in which:

FIG. 1 shows the location registration for a radiotelephone subscriberstation, given a change of location from one radio cell to another radiocell, and

FIG. 2 shows the connection setup to a radiotelephone subscriber stationby means of transmission of a radio paging message to the last-usedradio cell.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 snows, in a schematic switching diagram, the locationregistration given a change of location of a mobile radiotelephonesubscriber, with its associated radiotelephone subscriber station MS,from a radio cell C1 to a radio cell C2 in a digital mobileradiotelephone network constructed from a plurality of radio cells. Aprocedure for the start of the location registration of theradiotelephone subscriber station MS is thereby initiated as soon as themobile radiotelephone subscriber moves from a radio cell C1 into the newradio cell C2, and is thereby served by a new subscriber database NVLRin place of a previous subscriber database OVLR. In the decentralsubscriber databases OVLR and NVLR, the subscriber data of mobileradiotelephone subscribers who are currently moving in a location areaallocated to the subscriber database are temporarily stored for theduration of the stay. The subscriber data of all mobile radiotelephonesubscribers registered in the mobile radiotelephone network are storedcentrally in a subscriber database HLR, which can be accessed both bythe previous decentral subscriber database OVLR and also by the newdecentral subscriber database NVLR. A mobile switching center MSC1 or,respectively, MSC2, which are interconnected, is connected to eachdecentral subscriber database OVLR or, respectively, NVLR. The mobileswitching center MSC1, MSC2 respectively overtakes theswitching-oriented functions during the connection setup in theassociated location areas. The mobile switching center MSC1 is connectedwith a base station control BSC1 that can serve several base transceiverstations in the location area. Each radio cell of the location areacomprises a base transceiver, in order to send or, respectively, receivesignals via the air interface. In the present example, the basetransceiver station BTS1 is arranged in the radio cell C1. A basestation controller BSC2, for supervising the base transceiver stationsprovided in the corresponding location area, is likewise connected withthe mobile switching center MSC2. In the present example, a basetransceiver station BTS2, for transmission and reception of the signalstransmitted through the air in the radio cell C2, is located in theradio cell C2.

If it is determined by the radiotelephone subscriber station MS, bymeans of the evaluation of adjacent base transceiver stations, that dueto the change of the radiotelephone subscriber station from radio cellC1 to radio cell C2 the items of information in the subscriber databasesconcerning the current location of the mobile radiotelephone subscriberare to be replaced, the radiotelephone subscriber station MS transmits amessage LU (Location Update). The message LU is received by the basetransceiver station BTS2 of the new radio cell C2, and is forwarded tothe new decentral subscriber database NVLR via the base stationcontroller BSC2 and the mobile switching center MSC2. With the messageLU, a temporary mobile radiotelephone subscriber identifier TMSI istransmitted for the identification of the mobile radiotelephonesubscriber, and a location area identifier LAI is transmitted for theidentification of the location area to which the radio cell C2 belongs.In addition to these items of information, a cell identifier CI2, whichidentifies the current radio cell C2 in which the radiotelephonesubscriber station MS is currently located, is concurrently sent by theradiotelephone subscriber station MS, and is stored in the new decentralsubscriber database NVLR.

The storing of the cell identifier CI2 ensues together with aninternational subscriber identifier IMSI that identifies the mobileradiotelephone subscriber, and that requests the new subscriber databaseNVLR from the previous subscriber database OVLR. For this purpose, thetemporary mobile radiotelephone subscriber identifier TMSI is sent tothe old subscriber database OVLR. Besides the international mobileradiotelephone identifier IMSI, the location area identifier LAI isentered in the subscriber database NVLR. For the international mobileradiotelephone subscriber identifier IMSI and the location areaidentifier LAI, there exists in the decentral subscriber database NVLR alist of the last-used radio cells, which can be recognized by the storedcell identifiers CI2, CIx . . . CIy. Together with the cell identifiersCI2 . . . , the associated times of the transmission of the cellidentifiers CI2 . . . can be registered in the subscriber database NVLRunder the international mobile radiotelephone subscriber identifier IMSIand under the location area identifier LAI. In the present example, thecorresponding times TCI2, TCIx . . . TCIy belong to the cell identifiersCI2, CIx . . . . CIy.

For a different international mobile radiotelephone subscriberidentifier IMSI′ and a different location area identifier LAI′, cellidentifiers CI1, CI3 . . . are stored in the subscriber database NVLRwith the associated times TCI1, TCI3 in the sequence of the last-usedradio cells. With the stored times, an item of information is obtainedfor the improvement of the hit certainty with which the mobileradiotelephone subscriber can successfully be found in a determinednumber of radio cells by means of the radio paging message.

After the execution of an authentification with which the accessauthorization of the mobile radiotelephone subscriber to the mobileradiotelephone network is monitored, the new subscriber database NVLRrequests the subscriber data of the mobile radiotelephone subscriberfrom the central subscriber database in the request REQ. The subscriberdatabase HLR sends the corresponding subscriber data DAT back to therequesting subscriber database NVLR, and initiates, by means of thetransmission of a message CC to the previous subscriber database OVLR,the erasing of the old subscriber data entered therein. The newsubscriber database NVLR assigns the mobile radiotelephone subscriber anew temporary mobile radiotelephone identifier TMSI′, which istransmitted to the radiotelephone subscriber station MS in the radiocell C2 via the mobile switching center MSC2, the base stationcontroller BSC2 and the base transceiver station BTS2.

FIG. 2 shows, in a block switching diagram, the connection setup givenan incoming call in the mobile radiotelephone network PLMN, said callhaving been initiated by a subscriber SA of a public telephone networkPSTN or of a service-integrating communication network ISDN. In thepresent example, the called mobile radiotelephone subscriber, with hisradiotelephone subscriber station MS, is located in the radio cell C2 ofa location area comprising several radio cells, said area beingidentifiable on the basis of an associated location area identifier. Thecalling subscriber SA, who as a rule does not know the current locationof the mobile radiotelephone subscriber, dials a call number MSISDN, bymeans of which the mobile radiotelephone subscriber can be reachedeverywhere in the mobile radiotelephone network PLMN. By transmittingthe radio paging message (paging), it is brought about that the mobileradiotelephone subscriber registers himself in the network with hisradiotelephone subscriber station MS. The subscriber call number MSISDNof the mobile radiotelephone subscriber is received by a mobileswitching center GMSC, which is arranged in the mobile radiotelephonenetwork PLMN at the interface to other communication networks. From theincoming subscriber call number MSISDN, the mobile switching center GMSCdetermines the correct central subscriber database HLR for the calledmobile radiotelephone subscriber, and sets up a signaling connectionthereto. On the basis of the signaling connection established, a requestINT (interrogation) is directed to the decentral subscriber database VLRin whose allocated location area the mobile radiotelephone subscriber iscurrently located. As a response to the request, the subscriber databaseVLR sends a mobile subscriber roaming number (MSRN) back to the centralsubscriber database HLR, which in turn forwards this mobile subscriberroaming number MSRN to the mobile switching center GMSC. On the basis ofthe incoming mobile subscriber roaming number MSRN, the mobile switchingcenter GMSC sets up a connection to a further mobile switching centerMSC, which is connected with the subscriber database VLR that isresponsible for the called mobile radiotelephone subscriber.

Since the mobile switching center MSC still does not know the mobileradiotelephone subscriber up to this time, this center requests from itssubscriber database VLR the subscriber data of the mobile radiotelephonesubscriber that are required for the connection setup, on the basis of amessage RE. The decentral subscriber database VLR thereupon supplies theinternational mobile radiotelephone subscriber identifier IMSI and thecell identifier CI2 for the identification of the last-used radio cellC2 and, if warranted, additional cell identifiers of radio cells thatare adjacent to the radio cell C2 in the known location area. On thebasis of the international mobile radiotelephone subscriber identifierIMSI and cell identifier CI2 transmitted to the mobile switching centerMSC, the mobile switching center MSC causes the transmission of a radiopaging message PB (paging broadcast) to the radio cells C2 identified bythe cell identifier CI2, and, if warranted, to the radio cells Cx . . .. Cy adjacent thereto. The paging broadcast PB is transmitted to theradiotelephone subscriber station MS by means of the responsible basestation controller BSC1 and the base transceiver station BTS2 arrangedin the radio cell C2. Adjacent radio cells Cx . . . Cy receive thepaging broadcast PB in corresponding manner via the base stationcontroller BSCx and the associated base transceiver station BTSx, etc.

For the case in which the radiotelephone subscriber station MS of thecalled mobile radiotelephone subscriber in the known location area isstill located in the last-used radio cell C2, the radiotelephonesubscriber station MS sends a response message PR (paging response) backto the mobile switching center MSC. If one of the radio cells Cx . . . .Cy adjacent to the last-used radio cell C2 contains the calledradiotelephone subscriber station MS, the sending back of the pagingresponse PB ensues correspondingly via the corresponding radioinstallations, consisting of a base transceiver station and a basestation controller. If the radiotelephone subscriber station MS does notrespond to a paging that was directed to the last-used radio cell or toseveral last-used radio cells and, if warranted, to the radio cellsrespectively adjacent thereto, the paging broadcast PB is transmitted bythe mobile switching center MSC to all radio cells of the location area.In the transmission of the paging response PR from the calledradiotelephone subscriber station in one of the radio cells of thelocation area, the cell identifier is again concurrently sent for theidentification of this radio cell in which the radiotelephone subscriberstation MS is present. In the present example, the paging response PRthus contains the cell identifier CI2 of the last-used radio cell C2,since the radiotelephone subscriber station MS is located therein.

The cell identifier for the identification of the current radio cell ina location area, which identifier can be transmitted without additionalsignaling traffic, enables an effective paging, in which the pagingmessage is sent either to the last-used radio cell or to severallast-used radio cells, and, if warranted, to the radio cellsrespectively adjacent thereto. Especially for radiotelephone subscriberstations having rapidly successive interactions with the mobileradiotelephone network, e.g. in the transmission of data packetsaccording to a separate packet data service (general packet radioservice) in the mobile radiotelephone network, or given stationaryradiotelephone subscriber stations that are used by the radiotelephonesubscriber as replacements for wire-bound stationary network subscriberstations, the present invention has the advantage of a reduction of thesignaling load in the paging of the radiotelephone subscriber stations,and an increase of the paging capacity in the respective location area.In addition, the cell identifier for the identification of therespective radio cell can be derived without increasing the signalingload in the mobile radiotelephone network. The additional memory expensefor the registration of the cell identifiers, including the associatedtimes at which transmission takes place into the respective decentralsubscriber databases, can thereby be kept within limits according to thenumber of radio cells and the size of the location area. The method forthe transmission of data packets according to the packet data service ina mobile radiotelephone network is specified for example in the Germanletters patent DE 19 524 659 C1

The invention is not limited to the particular details of the method andapparatus depicted and other modifications and applications arecontemplated. Certain other changes may be made in the above describedmethod and apparatus without departing from the true spirit and scope ofthe invention herein involved. It is intended, therefore, that thesubject matter in the above depiction shall be interpreted asillustrative and not in a limiting sense.

1. A method for sending a radio paging broadcast to radiotelephonesubscriber stations of mobile radiotelephone subscribers of a cellularlyconstructed mobile radiotelephone network, comprising the steps of:managing locations of the radiotelephone subscriber stations by locationareas that consist respectively of at least one radio cell and that areidentifiable by a location area identifier; calling radiotelephonesubscriber stations in a location area by transmission of a radio pagingbroadcast; sending, in a transmission of messages respectively sent by arespective radiotelephone subscriber station, a transmitted cellidentifier that identifies a current radio cell in which the respectiveradiotelephone subscriber station is currently located, the transmittedcell identifier being sent in addition to the location area identifier;storing the transmitted cell identifier in a subscriber database of themobile radiotelephone network; entering the transmitted cell identifierin a list of cell identifiers comprising both the transmitted cellidentifier and retained cell identifiers which were formerly transmittedcell identifiers, thereby retaining transmitted cell identifiers; andsending the paging broadcast to at least one cell listed in the list ofcell identifiers.
 2. The method according to claim 1, wherein the radiopaging broadcast is transmitted to a last-used radio cell determined bythe stored cell identifier.
 3. The method according to claim 1, whereinthe radio paging broadcast is transmitted to several last-used radiocells that are determined by the stored cell identifiers.
 4. The methodaccording to claim 1, wherein the radio paging broadcast is transmittedto a last-used radio cell, and, in addition, to radio cells adjacentthereto that are determined by the stored cell identifiers.
 5. Themethod according to claim 1, wherein to increase a certainty of a hitduring calling of the respective radiotelephone subscriber station, atime of transmission of the cell identifier is stored in the subscriberdatabase, together with the cell identifier.
 6. The method according toclaim 1, wherein if a paging response message that can be sent back by aradiotelephone subscriber station fails to appear, the radio pagingbroadcast is transmitted to all radio cells of a location area.
 7. Themethod according to claim 1, wherein the cell identifier and a time oftransmission of the cell identifier are stored in a decentral subscriberdatabase that is responsible for the radiotelephone subscriber stationslocated in an allocated location area.
 8. The method according to claim1, wherein the cell identifier and a time of transmission of the cellidentifier are stored in the subscriber database, together with asubscriber identifier that identifies the mobile radiotelephonesubscriber.
 9. The method according to claim 1, wherein the cellidentifier is respectively concurrently sent in data packets that aretransmitted in the mobile radiotelephone network according to a datapacket service.
 10. A system for transmitting a radio paging broadcastto radiotelephone subscriber stations of mobile radiotelephonesubscribers in location areas of a cellularly constructed mobileradiotelephone network, whereby the location areas respectively managelocations of the radiotelephone subscriber stations, and respectivelyconsist of at least one radio cell, and are identifiable by a locationarea identifier, comprising: the radiotelephone subscriber stationshaving means for transmitting messages that respectively contain, inaddition to the location area identifier, a transmitted cell identifierthat identifies a current radio cell in which a respectiveradiotelephone subscriber station is currently located; and the mobileradiotelephone network having at least one subscriber database in whichthe transmitted cell identifier is entered in a list of cell identifierscomprising both the transmitted cell identifier and retained cellidentifiers which were formerly transmitted cell identifiers, and thetransmitted cell identifier is retained, the radio paging broadcastbeing sent to at least one cell listed in the list of cell identifiers.11. The system according to claim 10, wherein the mobile radiotelephonenetwork has means for transmitting the radio paging broadcast to alast-used radio cell that is determined by the entered cell identifier.12. The system according to claim 10, wherein the mobile radiotelephonenetwork is provided with means for transmitting the radio pagingbroadcast to several last-used radio cells determined by the enteredcell identifiers.
 13. The system according to claim 10, wherein themobile radiotelephone network has means for transmitting the radiopaging broadcast to a last-used radio cell, and, in addition, to radiocells adjacent thereto as determined by the entered cell identifiers.